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Passengers said a tour bus swerved for several minutes before a deadly crash on Highway 38 near Big Bear. The tour operator released a statement after the crash that killed at least seven people. Annette Arreola reports for Today in LA on Monday Feb. 4, 2013. (Published Monday, Feb. 4, 2013)

A tour bus swerved for several minutes Sunday evening, crashing into two other vehicles before flipping on a two-lane mountain road east of Los Angeles in a rollover that killed at least seven people and injured 38 others.

After inspecting the interior of the bus Monday afternoon, California Highway Patrol investigators revised the total number of victims killed to seven. Initial estimates were that eight people were killed.

Crash investigators at the location -- the crash occurred at about 6:30 p.m. on Highway 38 near Mentone, about 80 miles east of Los Angeles -- are attempting to determine what led to the deadly crash.

"Speed was probably a factor," said CHP Officer Mario Lopez. "We do not know if there was a mechanical failure or driver error. That's what investigators at the scene are going to determine."

A victim's family member identified some of the passengers as medical students from Tijuana, Mexico. They were returning from a skiing and snowboarding trip in Big Bear when the bus began swerving and the driver, who survived the crash, reported a problem with the brakes.

The bus collided with a Saturn sedan and Ford truck that was towing a trailer. Aerial video showed debris scattered across the two-lane road and the pickup with significant damage on the side of the road.

The pickup driver suffered major injuries, and three people in the Saturn suffered minor injuries, according to the California Highway Patrol.

Betty Harvey was traveling down Highway 38 when she saw the bus speed past.

"I saw a headlight in the my rear-view mirror," said Harvey. "I moved over and he went flying past. He was swerving all the way down."

Passengers told NBC4 the bus swerved for about three minutes before it flipped near Bryant Street (map).

Authorities plan to retrieve a passenger list from inside the bus Monday morning. Investigators are waiting to stabilize the vehicle, which is on an embankment, before entering.

At least two deceased passengers remained on the bus Monday morning. The number of casualties might change during the investigation, Lopez said.

About 40 people were aboard the bus, owned by Scapadas Magicas LLC. At least 15 victims remained hospitalized Monday morning.

"We've been unable to go inside the bus," Lopez said. "Once we can do that, we can identify the individuals involved in this."

Officials with the coroner's office remained at the location Monday (AP photo embedded right). National Transportation Safety Board investigators were en route to the site.

Highway 38 was expected to remain closed during the investigation Monday.

Carrier Inspections Show Violations

Scapadas Magicas has offices in National City, Calif. Federal transportation records show that the company is licensed to carry passengers for interstate travel. No crashes involving a company owned bus have been reported in the past two years, but several violations were reported during inspections, according to federal records.

The tour operator, INTERBUS Tours, released a statement Monday morning on its Facebook page.

"INTERBUS Tours and its team are working to support our clients and their families that unfortunately suffered an accident coming down from the mountains of Big Bear in San Bernardino CA. Interbus staff are located in offices and in the hospitals where we know the authorities transferred the wounded."